This invention relates to the processing of metals, and more particularly to an apparatus for generating a vortex in a melt of molten metal to facilitate the submergence of solid metal into that melt.
The lightweight metal aluminum possesses characteristics which render it suitable for use in many manufactured goods, and much of the aluminum used in such goods derives from aluminum scrap. Typically the scrap is reduced to a melt in a furnace, and the melt in turn is cast into ingots, which are sold to manufacturers of aluminum products.
The typical aluminum furnace contains an enclosed chamber which holds a melt and above the melt has burners which direct flames over the melt to produce enough heat to maintain the melt in a molten condition. The enclosed chamber communicates with a pumping well which in turn communicates with a charging well which may communicate with another well or the main-chamber itself, with this communication being provided by ports, all of which are below the upper surface of the melt. The pumping well contains a pump which circulates the molten aluminum, drawing it from the main chamber into the pumping well and forcing it into the charging well and thence back into the main chamber. The upper surface of the melt is exposed in the charging well, and here the scrap is introduced into the melt where it liquifies to become part of the melt.
Beverage cans, being for the most part thinly drawn aluminum, do not sink readily into the melt. Indeed, if left undisturbed, they will merely float on the melt or the dross on top of it. Instead of becoming molten aluminum, the scrap aluminum oxidizes in the presence of the intense heat and becomes aluminum oxide, which is dross. Thus, unless the lightweight aluminum scrap is quickly submerged in the melt, and thereby isolated from the ambient air, it stands a good chance of merely adding to the dross instead of becoming molten aluminum.
In order to effectively submerge the aluminum scrap, it is not uncommon to equip the charging well of an aluminum furnace with an impeller which rotates in that well to create vortex. The lightweight scrap aluminum is simply dumped into the vortex where the currents immediately carry that scrap beneath the surface. However, the impeller requires a large framework to support it in a cantilevered condition over the well, and the framework in turn requires a massive foundation. While the framework has components which shift relative to each other to raise and lower the impeller and to even remove it completely from the well, the framework and its foundation, being located adjacent to the well, interfere with the loading and maintenance of the well.
In the present invention, an aluminum furnace has a charging well in which an impeller rotates, but the impeller, instead of being supported on a complex framework and massive foundation, is suspended by means of a trolley from an overhead track.
Less clutter exists along the charging wall, and it is thus more accessible for both charging and maintenance. The impeller is carried by an assembly which raises and lowers it. The well possesses a somewhat cylindrical configuration and includes both inlet and outlet ports, all arranged to complement the impeller in establishing and maintaining a suitable vortex. The configuration of the impeller is particularly suited for establishing and maintaining the vortex.